2,5-二甲基-1,3,4-噻二唑激发态结构动力学的共振拉曼光谱研究

Resonance Raman Spectroscopic Investigation of Excited State Structural Dynamics of 2,5-dimethyl-1,3,4-thiadiazole

获得了2,5-二甲基-1,3,4-噻二唑(DMETD)在乙腈、甲醇和水中的紫外吸收光谱以及三种溶剂中不同激发波长下的共振拉曼光谱,并结合含时密度泛函TD-B3LYP/6-311++G(d,p)计算对DMETD的短时结构动力学进行了研究。通过固态的FT-Raman、FT-IR光谱和DFT计算指认了DMETD在溶剂中的共振拉曼光谱,并对DMETD共振拉曼光谱的强度模式进行了分析。结果表明DMETD在气相和溶剂中的跃迁主体都是π→π*。溶剂模型计算发现溶剂的极性对拉曼强度无影响。这样,DMETD在Franck-Condon区域活性振动模大致可以指认为7个基频v8,v12,v15,v17,v22,v23和v27以及它们的倍频和组合频,C=N和N-N伸缩振动占据了对拉曼强度的主要部分,说明S2激发态结构动力学也主要沿这两个坐标进行。

The ultraviolet absorption spectra and resonance Raman spectra of 2, 5-dimethyl-1,3,4- thiadiazole （DMETD） were obtained in acetonitrile, methanol and water. Short-time structural dynamics of DMETD was studied in combination of density functional theory TD-B3LYP/6-311 ＋＋G （d, p）. Resonance Raman spectra of DMETD in the solvents were identified through solid-state FT-Raman, FT-IR spectrum and DFT calculation. Besides, the intensity mode of Resonance Raman spectra of DMETD was analyzed. The results show that transition subject of DMETD in gas phase and solvents is x→x ＊. Solvent model calculation indicates that the polarity of solvents has no influence on Raman intensity. Thus, the active vibrational mode of DMETD in the Franck-Condon region can be identified as 7 fundamental frequencies （v8, v12, v15, v17, v22, v23 and v27）, their frequency doubling and combined frequencies. C=N and N-N stretching vibrations occupy the main part of Raman intensity. This indicates that Sz excited state structural dynamics is mainly along the two coordinates.